Method of making bubble caps



g- 1941- w. R. GRUNOW METHOD OF MAKING BUBBLE CAPS Filed Sept. 22, 1957 [WE M012. T/LLM (Q M BY Md 1 M 4 ATTORNEYS.

Patented Aug. 12, 1941 METHOD OF MAKING BUBBLE CAPS William R. Grunow, Harrison Township, Allegheny County, Pa., assignor to Allegheny Ludlum Steel Corporation, a corporation of Pennsylvania Application September 22, 1937, Serial No. 165,062

1 Claim.

My present invention relates to bubble caps for use in connection with the treatment of hydrocarbons and natural gases as well as for use in absorption operations such as are generally carried out in industrial chemical processes wherein gases or vapors are bubbled through absorbing or reacting media often in countercurrent fiow such as in acid manufacture, etc.

In connection with the treatment of liquid hydrocarbons it is common in this art to pass such liquid hydrocarbons through a tower usually of cylindrical shape which is provided with a plurality of vertically spaced perforated trays. A short length of pipe or tube is associated with each of the perforations in such trays and a bubble cap is placed on the top of each such pipe or tube for a purpose well known in this art.

It has been common to make these bubble caps, many hundreds of which are used in a single tower, from cast iron, cast steel or other materials. These bubble caps have certain disadvantages which are recognized in the field such as undue weight, susceptibility to breakage and corrosion and consequent short life. In attempts to improve bubble caps, the art has proposed to make them from alloys having greater corrosion resistance and less weight than cast iron or steel and more and more the industry is turning to these alloy caps. While such are a material improvement from the standpoint oi weight and corrosion, their use has inwithout annealing-operations.

troduced another disadvantage, namely, that of I mounting cost since alloy bubble caps are considerably mor expensive than cast iron or steel bubble caps.

.The production of alloy bubble caps from such corrosion-resistant materials as chromium steel and various modifications thereof has in itself presented diiliculties. For example, one form of bubble cap made of alloy steel is produced in the shape of a frusto-pyramid. In order to make such bubble caps the practice has been to cut out or stamp a series of one-piece Maltese crosses from relatively wide sheets or strips of such alloy steel, to shape or otherwise form the Maltese crosses into frusto-pyramidal bubble caps and then to weld the edges together in such shape. In cutting out these one-piece Maltese crosses from alloy steel sheets or strips a relatively large percentag of scrap material is produced due to the odd shape of a Maltese cross with the further result that the cost of the bubble caps is inordinately increased because of this scrap production.

Another common form of bubble cap has been that of a cylinder with a closed top. In making this form of bubble cap by known methods, a large circular piece has'been cut from the proper material and has then been formed into a bubble cap by. a series of drawing-with or This too has had a double disadvantage in that a relatively large proportion of the material used for making the caps becomes scrap and the drawing and annealing operations are comparatively expensive. Thus the art has not been able to make alloy steel bubble caps economically or at moderate costand this has had a deterrent effect upon the use of alloy steel for this purpose.

One of the objects of my present invention is to make possible the production of bubble caps of the frusto-pyramidal (with four, six or any other suitable number of sides) type from alloy steel of any desired composition at greatly-reduced cost andhence to increase the extent of use of alloy steel in the production of bubble caps with the consequent advantages thereby accruing.

Another object of my invention resides in the production of bubble caps from alloy steels of any desired composition in such a manner as to obviate the production of comparatively large percentages of scrap metal and thereby to produce the caps fora fraction of the present cost of such alloy caps.

A further object of my invention resides in the production from alloy steel of suitable composition and from strip or sheet metal of reduced dimensions separate parts or pieces which can be simply assembled and welded to produce bubsembled and welded. into final form.

More specifically, an object of my invention resides in producing from alloy strip or sheet metal a series of identical pieces or parts, while at the same time forming in certain of them openings or cut-away portions which are required for the eflicient operation of the bubble caps, and then in welding these pieces or parts together to form the completed bubble cap. This object also has a corollary the advantage that if it is so desired the bubble cap parts prior to their being welded can be shipped or handled in the flat simply and economically and can be shipped or transported at reduced cost due to the fact that much less space is required for the same. Then welding can be effected in the field, on the job or by fabricators.

Other and further objects and advantages will either be understood by those skilled in this art or will be apparent or pointed out hereinafter.

In-. the accompanying drawing wherein like numerals designate corresponding parts throughout the various views:

Figure 1 illustrates a strip of metal of any desired composition indicating how the sides of a bubble cap are produced therefrom;

Fig. 2 represents a strip of metal of suitable composition indicating how the top pieces of a bubble cap are produced therefrom;

Fig. 3 is an exploded view showing the parts of a frusto-pyramidal bubble cap as produced from the strips of Figures 1 and 2 but before complete assembly and welding of the same;

Fig. 4 illustrates in perspective a frusto-pyramidal bubble cap in its completed form as pro duced from the parts shown in Fig. 3;

Fig. 4a is a perspective view of a six-sided frusto-pyramidal bubble cap.

Fig. 5 is a fragmentary vertical elevation through a hydrocarbon, natural gas or chemical treating tower illustrating the general nature of such a tower and the manner in which the bubble caps are therein utilized.

Referring first to Fig. 5 which illustrates a fragment of a treating tower in which bubble caps are commonly used, the numeral l indicates a cylindrical metal shell or the like which makes up the body of the tower. One of the vertically spaced trays therein is indicated by the numeral II and may be suitably secured to the metal shell III in any desired-or conventional manner such as by welding, riveting, or by providing suitable brackets l2 secured to the shell for the purpose of supporting such trays circumferentially. It will be noted that each tray II has a number of apertures or perforations l3 therethrough of any desired size and spacing and that associated with each such opening or perforation is a short piece of tube or pipe l4 commonly called a chimney. The structure so far recited may be considered conventional and explanatory and does not form per se a part of the present invention.

Disposed over each short pipe'or tube I4 is a bubble cap indicated by the numeral l of the form and construction shown in Fig. 4 but which may be any of the types or forms herein disclosed. These bubble caps are made of suitable alloy steel or any desired alloy composition which has the proper characteristics particularly as to corrosion resistance as hydrocarbonaceous and many other materials which are passed through such a tower are strongly corrosive. It will further be noted that a certain amount of liquid hydrocarbon or other absorbing medium rests on each tray H and the level of such is indicated by the line l6.

In utilizing such a tower the natural gases or other materials either ofhydrocarbonaceous or other nature or origin are' passed upwardly through the tower and due to the construction thereof the same must necessarily pass upwardly through the short pipes or tubes (chimneys) l4 and then must impinge upon the under side of the bubble cap tops and since hydrocarbonaceous gas or vapor material is admitted under some pressure to the tower that material is forced through the openings I! in the bubble caps and hence bubbles through the liquid hydrocarbon or other absorbing material on the trays, whence the term bubble caps. It will be understood from Fig. 5 that the hydrocarbonaceous or other material passes upwardly from tray to tray and finally passes out through the top of the tower and that during its passage through the tower the desired treatment has been effected such as absorption, reaction, etc. In the case of natural gas, for example, this involves the removal of contained or entrained liquid hydrocarbons therefrom and a particular use of the present invention is in the production of so-called natural gasoline or other hydrocarbonaceous products from natural gas and other naturally occurring gaseous compositions. The tower and/or the bubble caps may, however, be used wherever it is desired to extract or to absorb certain fluid components of materials and hence is not limited in its use to the particular fields referred to.

Referring now to Figs. 1 to 4, inclusive, it will be apparent that a frusto-pyramidal bubble cap l5 of the construction illustrated in Fig. 4 is produced by a series of very simple and relatively inexpensive operations. The strip of metal l8 shown in Fig. 1 and which may be of any desired or preferred composition is of indeterminate length and has a width equal to the slant height of the bubble cap of Fig. 4. That is to say, the distance A from the lower edge to the upper edge of the strip of Fig. 1 is equal to the distance A from the lower edge to the upper edge of the side portions of the completed bubble cap measured along the surface of the cap.

This strip I8 is cut or severed on the dotted lines I 9 to form a series of pieces 20 of trapezoidal form or nature. The term "trapezoidal" is herein used to designate and define pieces 20 even though such pieces are characterized by having their non-parallel sides equal. It will be understood that each such trapezoidal piece 20 forms a side piece of the bubble cap l5, as will be understood from Figs. 3 and 4 and preferably simultaneously with the severance of such trapezoidal pieces from the strip I 8 slots, holes or apertures 2| of any desired size, spacing and configuration are produced therein. It will be clear that since the trapezoidal pieces 20 as-produced from strip I 8 have their bases, i. e., the edges which form the bottom of the sides of the bubble cap, first along one edge of the strip and then along the opposite edge, alternately, the apertures or holes 2| are formed in a staggered relationship as will be clear from Fig. 1.

In producing such trapezoidal side pieces 20 I from the strip I8 of Fig. 1, it will be clear that the only scrap metal which is produced is constituted of the relatively small pieces 22 at each end of the strip and of course those small pieces which are produced when the apertures or slots 2| are made in the strip. This scrap, however, as compared with that produced by stamping Maltese crosses or producing pyramidal caps in any other known manner from a much wider strip of material which, in the case of the Maltese cross arrangement, must have'a minimum width equal to the sum of two sides and the top of the bubble cap, is quite small. Thus I have not only more fully and eiliciently utilized the alloy'material, but I have greatly simplified and cheapened the bubble cap itself without sacrifice of any of the desired qualities of such bubble cap.

It will be noted from Fig. 3 in particular that the frusto-pyramidal bubble. cap I5 is made up of four of the trapezoidal pieces 20 described in connection with Fig. 1 and one top piece 23 A series of these top pieces 23 is made from a separate strip of metal 24 of the same composition as the strip it of Fig. 1. The strip 24 of Fig. 2 has a width equal to one dimension of the top of the bubble cap and from such strip a series or succession of top pieces 23 is severed by cutting the strip along the dotted lines indicated at 25 thereon. Such an operation, i. e., the production of the top pieces. produces no scrap at all when the length of the strip is an even multiple of each top piece. Otherwise. a fractional piece of a top will be produced as scrap but this is negligible as compared with prior practice.

The pieces shown in Fig. 3 and resulting from the severing of the strips of Figs. 1 and 2 along the dotted lines are flat and ready to be assembled and welded to produce the structure of Fig. 4. It is, I believe, a fact that many of the installations or plants in these fields have facilities for assembly and welding operations, hence I may ship these separate flat pieces to the installation or plant in the field or to a fabricator and this can be done with minimum space requirements for transportation and hence at materially decreased transportation costs. The caps can readily be completed in the field, on the job, or by fabricators, but if ,I so desire, I may complete their formation prior to shipment.

Whether made up on the job or at the place of manufacture, four of the trapezoidal side pieces 20 and one rectangular or square top piece 23 are assembled and welded together with the use of welding material having the same composition as the alloy or metal of the bubble cap. While this is not absolutely essential in all cases. it has well recognized advantages which the art appreciates. I may however, use welding material of any composition suitable for the use in question. The welds will be clear from Fig. 4 in particular and are indicated thereon by the numerals 2B. As illustrated. the weld extends around the top edges of the trapezoidal side pieces where they meet, abut or adjoin the edges of the top piece and part way down the sides or corners to a point approximately at, or somewhat below, the upper level of the openings 21. It is unnecessary to weld the sides or corners all the way to the bottom, because it is not only immaterial whether there is some leakage through the lower corner portions 2? of the cap, but such is an actual advantage, in eii'ect providing additional openings.

As previously indicated, frusto-pyramldal bubble caps within the present invention may be made with four, six or any other desired number of sides. A six-sided bubble cap is shown at i5a in Fig. 4a and is made up of six trapezoidal side pieces 20a provided with openings 2 (a and a hexagonal top piece 23a welded together at 26a in the manner explained in connection with Figs. 3 and 4. It will be evident that in forming hexagonal top pieces 2302 some scrap will result but this is still far below that produced by prior practice. The side pieces 20a are made in accordance with Fig. 1.

I have described and illustrated my present invention in an illustrative rather than a limitative manner and it is to be understood that certain variations, modifications, substitutions and omissions may be made without departing from the principles herein set forth and so long as these fall within the spirit and terms of the appended claims, I deem all such to be a part of my present invention. I may, of course, maize a bubble cap of any desired or required size, shape,

configuration and composition and while I have illustrated preferred bubble caps of frustopyramidal types I am not limited thereto as other shapes can be also produced in accordance with this invention. While I have indicated that the bubble caps are preferably produced from alloy steel and more particularly from alloy steel containing a desired percentage of chromium, I am not limited to the precise composition of the metal, but may use any which will fulfill the requirements of any special use. It is within the purview of my invention to produce bubble caps from stainless steels; such as the 18-43 type and straight chrome type. the latter being characterized by a chromium content up to about 30%. e. g., 440%, with low carbon, phosphorus and sulphur and with the balance substantially all iron.

While I have illustrated and described bubble caps the parts of which are made from the same gauge material, another advantage of making multi-part caps as described resides in the fact that the tops can be made of heavier gauge or more resistant material, thus enabling the caps the better to withstand corrosion and erosion. Such is not possible in bubble caps made in accordance with prior practices.

While I have illustrated and described my present invention in connection with treating hydrocarbons or extracting liquid hydrocarbons from gases of various compositions, I do not intend to be limited thereto as the inventionmay be used in connection with other fields in chemistry, physics and metallurgy wherever the principles thereof find application as will be appreciated from the foregoing.

While I have illustrated and described the production of sides and top portions from strip or sheet material having a width ota single side or top piece respectively, it is within the purview of my invention to produce the separate bubble cap portions from strip or sheet material having a width equal to an even multiple of such sides and top portions and hence from which a plurality of sets of bubble cap pieces can be produced. That is to say, the strip 18 of Figure 1 may have a width equal to 2A, 3A, etc., and by the same token the strips 24, 28 and 32 may be twice, thrice or more times that of the respective bubble cap pieces produced therefrom.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

A method of making a bubble cap composed 01 a plurality of trapezoidal side pieces and a completing top piece with minimum scrap produc tion which comprises the steps of producing a strip of suitable metal of indeterminate length and having a width equal to the slant height of the bubble cap, severing said strip in such manner as to produce therefrom a plurality of trapezoidal pieces, adjacent edges of each pair of such pieces being formed by a single out forming openings in each such piece substantially simultaneously with the severing thereof, assembling the necessary number of pieces into a frustopyramidal bubble cap and welding the pieces to-- gether except at the lower corners thereof.

WIILIAM R. GRUNOW.

. CERTIFICATE OF CORRECTION. Patent no. 2,2 2,000; I August 12, 19in.

. WILLIAM R. GRUNQW.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction esfollowsz Page l, sec- 0nd column, line 52, after "has" insert as; and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25rd day of September, A. 1). 19in.

Henry Van Arsdale,

( Seal) 7 Acting Commissioner of Patents. 

